56 GASEOUS METABOLISM OF INFANTS. 



This method proved admirable for use with animals and was subse- 

 quently added by us to the respiration apparatus for infants. We have 

 in an earlier publication pointed out the advantages of securing such 

 records and have likewise given some characteristic tracings. 1 



The same principle has been applied to the bed calorimeter in use in 

 the Nutrition Laboratory. 2 For this apparatus, however, we have 

 recognized the fact that while infants when moving usually change the 

 center of gravity lengthwise of the body, the muscular movements of 

 adults are apt to be in a lateral rather than a longitudinal direction, so 

 that the center of gravity is changed across the body. Accordingly 

 the knife edges are placed on one side of the bed and spiral springs 

 on the other when used for adults, rather than at the foot or head as 

 when used with the crib or cage for infants or animals. 



Certain details of the crib suspension have already been given in 

 figure 2, but the exact connection between the crib and the tambour 

 is shown in figure 5. One end of the crib, L, rests on a knife edge, 0, 

 while the other is supported by the spiral spring, M. A tube pneu- 

 mograph, N, has its lower end attached to the crib, the upper end 

 being fastened to a stout support soldered to the wall of the respiration 

 chamber. The changes in tension of the air in the pneumograph are 

 transmitted through the tube to a tambour, P, whose pointer traces 

 the record upon the kymograph drum. A glass tee, T, with rubber tube 

 and pinchcock, serves to equalize the tension in the tambour if there 

 should be any permanent contraction or distention of the pneumograph. 



The careful and frequent testing of both the pneumograph and the 

 tambour for tightness is of practical importance. The pneumograph 

 being inside the respiration chamber, and connected by a rubber tube 

 to the outside, would obviously furnish a path for leakage of air out of 

 the chamber, provided a leak in both the pneumograph and tambour 

 should occur. Tests are readily made by immersing them in water 

 and employing slight pressure with the mouth on the connecting rubber 

 tube. The pneumograph is of the type regularly furnished by the 

 Harvard Apparatus Company, but for use in the infant chamber it is 

 somewhat shortened. The tambours, which are likewise supplied by 

 the Harvard Apparatus Company, are covered with very delicate 

 tambour rubber, which is liable to deterioration and should thus be 

 frequently renewed and tested. 



Benedict and Talbot, Am. Journ. Diseases of Children, 1912, 4, p. 129. 



2 After the observations reported in this publication had been completed, information was 

 received from Dr. Paul Roth, of Battle Creek, Michigan, that in recording the body movements of 

 men or women lying on beds, he had replaced the pneumograph with a small Politzer bulb, so 

 adjusted as to be somewhat compressed by the bed frame. The bulb was connected to the 

 tambour and kymograph. Preliminary tests made in the Nutrition Laboratory with the Politzer 

 bulb arrangement have shown that the results of the variation in pressure on the Politzer bulb by 

 variation in muscular activity are most satisfactory, not only with adults but also with small 

 animals — a fact of special interest in connection with the research on infants. Two serious 

 objections to the pneumograph, i. e., the danger of leaks through the rubber and the difficulty of 

 renewing the rubber, are thus obviated by the use of this bulb. A flexible rubber bulb of small 

 size is best used. 



